Where is Islamic State’s leader?

[...] in the fourth week of a U.S.-backed alliance’s pincer-like move to retake the northern Iraqi city, the whereabouts of the Islamic State chieftain are unknown — though a rare audio recording posted online last week by the militant group and attributed to him urged followers to fight to the death.

Al-Baghdadi and his senior lieutenants have been the targets of an intensive manhunt by Iraqi and U.S. forces working from land and air, but experts disagree on how and where Islamic State’s top leadership might seek to regroup and recoup — if they are still present in the city, and if they manage to survive the battle of Mosul.

Mosul’s inner precincts, which attacking forces have yet to penetrate, offered ample hideouts even before Islamic State fighters, during nearly 2½ years of occupation, constructed an intricate warren of defenses above and below ground, including tunnels, trenches and secret passageways.

Al-Baghdadi, believed to be 45, is an Islamic scholar who is considered a prime architect of Islamic State’s apocalyptic ideology and its code of systematic and gruesome punishments of so-called infidels in areas under the group’s control.